Crevices in the combustion chambers of piston engines are of interest to researchers for many reasons. As one example, combustion chamber crevices in internal combustion engines are significant contributors of hydrocarbon (HC) emissions. These crevices are identified as narrow regions of the combustion chamber into which the combustion flame does not reach. One such crevice is the gap between the piston and the cylinder wall. During the compression stroke, unburned charge is pushed into this crevice. The crevice is narrow enough to quench the flame front, leaving unburnt gases, so that during the power stroke, as the piston descends and the exhaust valve opens, these unburnt gases re-emerge in the exhaust.
To successfully achieve emissions goals, engine design and operation must account for the effects of combustion chamber crevices. To this end, efforts have been made to sample material in the piston crevices. Past sampling methods involve drawing the sample out through tubing connected to a hole through the piston near the piston rings. The tubing traverses the connecting rod and is carried by a specially designed linkage to the point where it exits the crankcase.